Magnetic properties and microstructure of Fe3B/Pr2Fe14B-type nanocomposite magnets with Co and Cr additions

Magnetic properties and microstructures of Fe3B/Pr2Fe14B-type nanocomposite magnets have been studied. Increasing content of Pr enhanced the coercivity at the expense of remanence and magnetic energy products in Pr4+xFe78-xB18 and Pr4+xFe76-xCr2B18 (x = 0, 0.5, 1) alloys. Combined additions of Cr and Co further improved hard magnetic properties. Optimum magnetic properties for the Pr4Fe71Co5Cr2B18 alloy with M-r (similar to 1.31 T), H-c (similar to 265 kA/m), (BH)(max) (similar to 115.4 kJ/m(3)) and Pr5Fe70Co5Cr2B18 alloy with M-r (similar to 0.97 T), H-c (similar to 385 kA/m), (BH)(max) (similar to 86.2 kJ/m(3)) were obtained after the samples were annealed at 628 and 658 degrees C for 10 min, respectively. Partially replacing Pr by Tb improved the overall magnetic properties to M-r (similar to 1.14 T), H-c (similar to 439 kA/m), (BH)(max) (similar to 119.4 kJ/m(3)) in Pr4Tb1Fe70Co5Cr2B18 alloy, and also reduced the optimum annealing temperature to 628 degrees C. Three-dimensional atom probe (3DAP) analysis showed that Cr is strongly partitioned in the Fe3B soft phase and Co has higher content in the Pr2Fe14B hard phase. (C) 2005 Elsevier B.V. All rights reserved.